1. Field of the Invention
The present invention relates to a driving mechanism that rotationally drives a pulley, and to an image forming apparatus comprising the same.
2. Related Art
Conventionally, an image forming apparatus such as a printer and a copying machine generally includes a photosensitive drum as an image carrier. The photosensitive drum includes: a photosensitive drum main body; and a shaft member that is disposed so as to penetrate the photosensitive drum main body in the rotation center of the photosensitive drum main body. A rotational driving force from a rotational driving unit is directly or indirectly transmitted to the shaft member, thereby rotationally driving the photosensitive drum.
As a driving mechanism that rotationally drives a photosensitive drum, for example, a driving mechanism is known, which includes a transmission belt extended over a pulley between an output shaft of a motor and a shaft member of a photosensitive drum in state in which the output shaft of the motor and the shaft member of the photosensitive drum are disposed in parallel with each other, and a rotational driving force of the motor is transmitted to the shaft member of the photosensitive drum via the transmission belt.
In such a driving mechanism, the transmission belt needs to be stably extended over the pulley in order to stably rotationally drive the pulley. If the transmission belt is not stably extended over the pulley, the transmission belt may meander or fall off the pulley. In contrast, the conventional art described above employs a configuration, in which a flange portion is created at the end portion of the pulley to restrict the transmission belt from meandering, and the end portion of the transmission belt is coated with resin to prevent abnormal noise from occurring when the end portion of the transmission belt and the flange portion are in contact with each other.
According to the conventional art described above, although the sliding noise of the transmission belt can be reduced, the end portion of the transmission belt is likely to slide. Moreover, in a driving mechanism (a speed reduction mechanism) that uses a transmission belt characterized in high rigidity and no engagement, the sliding at the end portion of the transmission belt may deteriorate the stability of the rotation of the pulley.
An object of the present invention is to provide a driving mechanism that transmits a rotational driving force via a transmission belt extended over a pulley, in which the transmission belt is stably extended over the pulley, and the pulley can be stably rotated.
In addition, another object of the present invention is to provide an image forming apparatus including the driving mechanism.